Detail of one of the external control vanes, located on one of the V-2's fins.
There's a tab screwed to both the body of the fin and the control vane,
presumably to prevent the vane from rotating while the missile was emplaced in
the exhibit space.
The state of the art at the time the V-2's engine was developed did not yet
support gimballing; rather, directional jet
vanes were placed in the engine's exhaust stream to help steer the
missile (along with these external control vanes on the fins).
I believe that each jet vane and corresponding external control vane were
controlled by a common drive motor.